1. Field of Invention
This invention pertains generally to photometric analyzers and, more particularly, to a photometric detector assembly for use in a photometric analyzer such as an inline optical sensor.
2. Related Art
U.S. Pat. No. 5,905,271 discloses an inline optical sensor which can be utilized in a wide variety of applications (e.g. spectrophotometers, calorimeters, turbidimeters, refractometers, and ultrasonic flow and particle sensing devices) for monitoring photometric the properties of a fluid product stream. Such instruments generally have a light source and a detector positioned on opposite sides of the product stream, with the light source directing a beam of light through the product stream to the detector. The light can be in the ultra violet, visible or near infrared spectrums, and the term light is used herein as including all three.
When inline photometric analyzers are used as a primary measurement source for controlling critical filtration and separation processes, particularly in the biotech and pharmaceutical fields, NIST traceable calibration standards must generally be used in order to comply with validation protocols and procedures. Such standards are typically in the form of filters which are placed between the light source and detector. These filters are subject to deterioration with use and exposure to the environment, and they must be re-certified periodically.
It is in general an object of the invention to provide a new and improved detector assembly for use in a photometric analyzer.
Another object of the invention is to provide a photometric detector assembly of the above character which has internal calibration filters.
These and other objects are achieved in accordance with the invention by providing a photometric detector assembly which includes a housing, means for passing an optical beam along a path through the housing to a detector, a NIST traceable calibration filter enclosed within the housing, and means operable externally of the housing for moving the filter into and out of the beam path between calibration and normal operating positions.